Alexander Ploss, PhD

At least 130 million people worldwide are chronically infected with hepatitis C virus (HCV). Infection frequently leads to advanced liver disease, including fibrosis, cirrhosis and hepatocellular carcinoma. Despite substantial efforts to develop antivirals directly blocking replication, treatment options remain limited. The current standard of care is only partially effective. A therapeutic or preventative vaccine does not exist. Currently, HCV associated liver transplantation is merely a palliative procedure due to universal infection of the graft after transplantation, often resulting in rapid fibrosis progression and subsequent graft failure. Even transient therapies inhibiting HCV cell entry could prevent graft reinfection and greatly improve the effectiveness of liver transplantation. Such therapeutic advances targeting this stage of the viral life cycle will require a much more solid understanding of HCV cell entry than is currently available. The development of treatment and prophylactic options has been hampered in part by the lack of immunocompetent, cost effective, robust, and reproducible small animal models for the virus. Besides humans, chimpanzees are the only species that is naturally susceptible to HCV infection. While experimentation in these large primates has yielded valuable insights, ethical considerations, limited availability, genetic heterogeneity, and cost limit their utility. To overcome roadblocks to HCV research in vivo, Dr. Ploss’ group has engineered an immunocompetent mouse model with genetically encoded susceptibility to the virus. Generation of HCV-permissive mice was facilitated by his recent discovery that species tropism at the level of entry is defined by two human molecules: CD81 and occludin (OCLN). Dr. Ploss has demonstrated that transient or stable expression of these entry factors in vivo renders mice susceptible to infection with diverse HCV genotypes. He has shown that viral uptake can be blocked by passive immunization strategies and that immunization of these animals induces humoral immunity and confers partial protection to heterologous challenge. He has also shown proof-of-principle for combining this system with gene knockout analysis to begin to dissect viral entry. He is now proposing to apply this system to genetically dissect HCV infection in vivo. Dr. Ploss aims to take advantage of existing repositories of mutant mouse strains to assess the impact of targeted gene disruptions on HCV infection. Combining mouse knockout technology with his genetically humanized mouse models therefore offers a unique opportunity dissecting HCV infection in the 3 dimensional context of the liver.